Deep level centers in electron-irradiated silicon crystals doped with copper at different temperatures

The effect of bombardment with energetic particles on the deep-level spectrum of copper-contaminated silicon wafers is studied by space charge spectroscopy methods. The p-type FZ-Si wafers were doped with copper in the temperature range of 645-750 C and then irradiated with the 10¹⁵ cm^-2 fluence of 5 MeV electrons at room temperature. Only the mobile Cu_i species and the Cu_PL centers are detected in significant concentrations in the non-irradiated Cu-doped wafers. The properties of the irradiated samples are found to qualitatively depend on the copper in-diffusion temperature T_diff. For T_diff > 700 C, the irradiation partially reduces the Cu_i concentration and introduces additional Cu_PL centers while no standard radiation defects are detected. If T_diff was below ∝700 C, the irradiation totally removes the mobile Cu_i species. Instead, the standard radiation defects and their complexes with copper appear in the deep-level spectrum. A model for the defects reaction scheme during the irradiation is derived and discussed. DLTS spectrum of the Cu-contaminated and then irradiated silicon qualitatively depends on the copper in-diffusion temperature. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)